Some conventional systems support wireless communication between wireless devices. Such communication systems range from national and/or international cellular telephone systems to the Internet, and to point-to-point in-home wireless networks. Each type of communication system is designed, and hence operates, in accordance with relevant communication standards. For instance, wireless communication systems may operate in accordance with one or more standards including, but not limited to, IEEE 802.11, Bluetooth, advanced mobile phone services (AMPS), digital AMPS, global system for mobile communications (GSM), code division multiple access (CDMA), local multi-point distribution systems (LMDS), multi-channel-multi-point distribution systems (MMDS), and/or variations thereof.
Depending on the type of wireless communication system, a wireless communication device, for example, a cellular telephone, two-way radio, personal digital assistant (PDA), personal computer (PC), laptop computer, or home entertainment equipment, communicates directly or indirectly with other wireless communication devices. For direct communications, also known as point-to-point communications, the participating wireless communication devices tune their receivers and transmitters to the same channel, or channels, and communicate via those channel(s). Each channel may utilize one or more of the plurality of radio frequency (RF) carriers of the wireless communication system. For indirect wireless communication, each wireless communication device communicates directly with an associated base station, for example, for cellular services, and/or an associated access point, for example, for an in-home or in-building wireless network, via an assigned channel or channels.
In order for each wireless communication device to participate in a wireless communication session, it may utilize a built-in radio, which comprises a receiver and/or a transmitter, and/or it may be coupled to an associated radio transceiver, for example, a station for in-home and/or in-building wireless communication networks, or a RF modem. The transmitter converts data into RF signals by modulating the data in accordance with the particular wireless communication standard. However, different communication systems may use different standards, for example, the IEEE 802.11 standard and the Bluetooth standard, which may share the same RF spectrum.
In order to alleviate signal interference from various RF devices sharing an RF spectrum with other communication systems, a transmission standard may allow frequency hopping where information is transmitted at various frequencies at different time instances. In this manner, the energy of the transmitted signal may be spread across the RF spectrum over the various channels allowed for communication. The advantage of frequency hopping may be that it spreads information across a wide band of frequencies. Therefore, signals transmitted by other systems using a portion of the same frequency spectrum may appear to be noise to only some of the frequencies used in frequency hopping. Similarly, only a portion of frequency hopping transmission may interfere with signals transmitted by other systems. Frequency hopping further provides resistance to multipath fading effects. Radio signals in some frequency bands are especially susceptible to multipath effects caused by the radio signal travelling over multiple paths with the reflections and direct signal combining either constructively or destructively at the receiver. With frequency hopping, data which is not successfully received on some frequency hops may be retransmitted on another frequency hop. In addition, with a technique called adaptive frequency hopping, the radio system can use avoid hop frequencies which are experiencing interference or multipath fading and utilize only those hop frequencies at which communications are successfully being received. A disadvantage of frequency hopping may be evident in cases where a receiving device may need to determine the frequency sequence used for frequency hopping. The receiving device may need to serially scan various channels for a sufficient period of time in order to determine the frequency hopping sequence. Since a receiver may have to acquire synchronization prior to receiving data, the longer it takes to acquire the synchronization, the period prior to which receiving of data may occur. For many applications, long periods prior to actual receiving of data may be intolerable.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.